Method for N,N-dicyanoethylating aminophenols

ABSTRACT

Pure N,N-dicyanoethylated aminophenols are prepared in good yields by refluxing an aminophenol with 2 mols of acrylonitrile in acetic acid as solvent. No added catalyst is required.

United States Patent [191 Jamieson METHOD FOR N,N-DICYANOETHYLATING AMINOPHENOLS [75] Inventor: Norman C. Jamieson, St. Louis. Mo. 73 Assignee: Mallinckrodt, Inc., St. Louis, Mo.

[22] Filed: June 21, 1973 [21] Appl. No.: 372,315

[52] US. Cl 260/465 E [51] Int. Cl. C07c 121/78 [58] Field of Search 260/465 E [56] References Cited UNITED STATES PATENTS 2,809.983 10/1957 Heininger 260/465 June 17, 1975 3,743,668 7/1973 Scully 260/465 Primary ExaminerLewis Gotts Assistant Examiner-Dolph H. Torrence Attorney, Agent, or Firm-John D. Pope, Ill

4 Claims, No Drawings 1 METHOD FOR N,N-DICYANOETHYLATING 'AMINOPHENOLS r BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the field of carbon chemistry and more particularly to the cyano'ethylation ofaminophenols. i

2. Description of the Prior Art Methods for preparing mon ocyanoethylated' aminophenols are known and suchproducts areknown to have many uses, For instance, seyeralpatents have been issued on processes for the cyanoethyl'ation of amines, e.g., US. Pat. No. 2,809,983; 3,231,601; 3,496,213, but all are directed at achieving monocyanoethylation. Although the use of acetic acid as a catalyst is well known in cyanoethylation proce dures, it is reported to give mixtures of monoand dicyanoethylated products (U.S.P. No. 3,496,213, column 1, lines 3539). High temperatures and pressures are also said to be necessary (loc. cit. column 1, lines 39-42) along with careful temperature control (lines 42-46). None of these previously known methods is suitable for the preparation of dicyanoethylated aminophenols.

SUMMARY OF THE INVENTION Among the objects of the present invention may be noted the provision of an improved method for the preparation of N,N-dicyanoethylated aminophenols; and the provision of methods of the character described which produce the pure dicyanoethylated product in good yields directly and easily without the need for added catalysts or high pressures. Other objects and features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the methods hereinafter described, the scope of the invention being indicated in the following claims.

According to the invention these objects are achieved by heating a mixture consisting essentially of an aminophenol, acrylonitrile, and glacial acetic acid at a temperature between about 25C. and the reflux temperature of the mixture. There should be approximately 2 mols or more of the acrylonitrile for each mol of the aminophenol, and the acetic acid content should be at least 50 percent by weight of the aminophenol. When the reaction is complete, the product may be recovered by quenching the reaction mixture with water provided the acetic acid content does not exceed about 70 percent of the aminophenol content. If excess acetic acid is present, it may be removed by distillation along with unreacted acrylonitrile prior to quenching the reaction mixture.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention is applicable to p-, or m-aminophenols and to substituted derivatives thereof provided the substituents do not themselves react with acrylonitrile.

Although a several molar excess of acrylonitrile can be used with no apparent oxy-cyanoethylation or other unwanted side reactions occurring, it is preferred to use between a percent and 50 percent excess. More specifically, a 20 percent excess is sufficient to allow for amount equal to half thewieght of the aminophenol was employed. Under these conditions,-simple quenching of the reaction mixture in water yielded the product as a light colored solid. In another embodiment a greater amount'of acetic acidis used. A distillation is -then necessary prior to quenching in water, but this method has the advantage that the distillate contains the excess acrylonitrile which can then be recycled. The distillation should be continued until there remains in the distillation flask an amount of acetic acid approximately equal to 60-70 percent of the weight of the starting aminophenol. This concentration yields the best crystalline form on subsequent quenching in water.

The reaction is essentially complete in eight hours, but reflux may be continued overnight or longer without deleterious effect.

The preparation is convenient as all the reagents are added at once and reflux temperatures are sufficient. No pressure equipment is needed. The product is isolated in good yield by simply quenching in water. The product is obtained as a light colored solid which may be recrystallized if desired, but the crude material is suitable for further reactions, e.g., hydrolysis to the diacid.

Even though aminophenols are sensitive to oxidation, the products obtained using the present invention are light-colored even when prepared under normal atmospheric conditions although an inert atmosphere (e.g., nitrogen) may be provided if desired.

The following examples illustrate the invention EXAMPLE 1 p-Aminophenol (109 g., 1.0 mole), acrylonitrile (125 g., 2.4 mole) and acetic acid (55 g.) were refluxed with stirring overnight. The mixture was then poured into cold water (500 ml.) with stirring. After stirring for one hour, the N,N-bis( 2-cyanoethyl)-p-aminophenol was collected as a light peach colored solid. Yield 183 g., 85 percent; m.p. 77.580C.

The product may be recrystallized from ethyl acetate or aqueous acetic acid. A sample purified by the latter method yielded light yellow needles, mp. -81C. Calcd. for C H N O: C 66.9, H 6.1, N 19.5 percent. Found: C 66.9, H 6.3, N 19.2 percent. N.m.r. and i.r. data confirmed the identity of the product.

EXAMPLE 2 Example 1 is repeated butm-aminophenol is substituted for the paminophenol. The product secured was N,N-bis(2-cyanoethyl)-mAminophenol.

EXAMPLE 3 Example I is repeated but o-aminophenol is substituted for the p-aminophenol. The product secured was N,N-bis (2-cyanoethyl)-o-aminophenol.

In view of the above, it will be seen that the several objects of the invetnion are achieved and other advantageous results attained.

As various changes could be made in the above methods without departing from the scope of the invention,

it is intended that all matter contained in the above de scription shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A method for preparing an N,N-dicyanoethylated aminophenol which comprises heating a mixture consisting essentially of an aminophenol at least 2 mols of acrylonitrile for each mol of the aminophenol, and glav cial acetic acid in an amount at least 50 percent by weight of the aminophenol, at a temperature between about 25C. and the reflux temperature of the mixture, and thereafter quenching the reaction mixture with water to precipitate a substantially pure dicyanoethylated phenol.

2. The method according to claim 1 wherein prior to quenching the reaction mixture excess acetic acid is distilled off until the remainder is approximately 60-70 percent by weight of the original aminophenol content.

3. The method according to claim 1 wherein the acetic acid content of the original mixture is 50-70 percent by weight of the aminophenol content.

4. The method according to claim 1 wherein the original proportion of acetic acid is in excess of percent by weight of the original aminophenol content and before quenching the proportion of acetic acid to original aminophenol content is reduced to not substantially more than 70 percent of said aminophenol content. 

1. A METHOD FOR PREPARING AN N,N-DICYANOETHYLATED AMINOPHENOL WHICH COMPRISES HEATING A MIXTURE CONSISTING ESSENTIALLY OF AN AMINOPHENOL, AT LEAST 2 MOLS OF ACRYLONITRILE FOR EACH MOL OF THE AMINOPHENOL, AND GLACIAL ACETIC ACID IN AN AMOUNT AT LEAST 50 PERCENT BY WEIGHT OF THE AMINOPHENOL, AT A TEMPERATURE BETWEEN ABOUT 25*C. AND THE REFLUX TEMPERATURE OF THE MIXTURE, AND THEREAFTER QUENCHING THE REACTION MIXTURE WITH WATER TO PRECIPITATE A SUBSTANTIALLY PURE DICYANOETHYLATED PHENOL.
 2. The method according to claim 1 wherein prior to quenching the reaction mixture excess acetic acid is distilled off until the remainder is approximately 60-70 percent by weight of the original aminophenol content.
 3. The method according to claim 1 wherein the acetic acid content of the original mixture is 50-70 percent by weight of the aminophenol content.
 4. The method according to claim 1 wherein the original proportiOn of acetic acid is in excess of 70 percent by weight of the original aminophenol content and before quenching the proportion of acetic acid to original aminophenol content is reduced to not substantially more than 70 percent of said aminophenol content. 